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Melcherite

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About MelcheriteHide

Formula:
Ba2Na2Mg[Nb6O19] · 6H2O
Originally approved as BaCa2MgNb6O19·6H2O, but formula was revised very soon after approval.
Colour:
Beige
Lustre:
Vitreous
Specific Gravity:
3.733 (Calculated)
Crystal System:
Trigonal
Name:
Named in honor of Geraldo Conrado Melcher (1924-2011), professor and head of the Department of Mining and Petroleum Engineering of the Polytechnic School of the University of São Paulo, Brazil, for his pioneering studies on Jacupiranga carbonatites.
A hexaniobate related to peterandresenite.

Melcherite has structural layers parallel to the xy plane that stack along the c-axis with simultaneous 1/3 [1 -1 0] displacement so as to produce a R lattice. The melcherite structure is built by layers of [(Ba,K)(O,H2O)9] polyhedra and the [Nb6O19]8− super-octahedron (Lindqvist anion) interconnected by [(Na,Ca)O6] polyhedra. Mg2+ cations are bonded to six water molecules each and are not associated with Lindqvist oxygen ions (Andrade et al. 2018]


Classification of MelcheriteHide

Approved
Approval Year:
2015
First Published:
2018

Physical Properties of MelcheriteHide

Vitreous
Transparency:
Transparent
Colour:
Beige
Streak:
White
Cleavage:
Perfect
on {001}
Density:
3.733 g/cm3 (Calculated)

Chemical Properties of MelcheriteHide

Formula:
Ba2Na2Mg[Nb6O19] · 6H2O

Originally approved as BaCa2MgNb6O19·6H2O, but formula was revised very soon after approval.
IMA Formula:
BaCa2MgNb6O19 · 6H2O

Chemical AnalysisHide

Empirical formulas:
Sample IDEmpirical Formula
1(Ba1.75K0.191.94(Na1.80Ca0.191.99(Mg0.96Mn0.02Al0.021.00Nb6.02O19.00·6H2O
2(Ba0.99K1.00 1.99(Na1.02Ca0.961.98(Mg0.95Mn0.051.00Nb6.02O19.00·6H2O

Crystallography of MelcheriteHide

Crystal System:
Trigonal
Class (H-M):
3 - Rhombohedral
Space Group:
R3
Cell Parameters:
a = 9.0117(6) Å, c = 23.399(2) Å
Ratio:
a:c = 1 : 2.597
Unit Cell V:
1645.64 ų
Z:
3
Morphology:
Irregular, tabular crystals up to 200 μm in maximum dimension.
Comment:
Chemical composition varies from Ba2Na2Mg[Nb6O19].6H2O to (BaK)(NaCa)Mg[Nb6O19].6H2O. Crystal data from the second composition

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
7.805(100)
7.410(14)
3.904(22)
3.852(21)
3.250(33)
2.952(13)
2.165(30)
2.160(12)
Comments:
From Type Description.

Type Occurrence of MelcheriteHide

General Appearance of Type Material:
As irregular, tabular crystals up to 200 μm in a vug in the carbonatite
Place of Conservation of Type Material:
Type material is deposited in the collections of the Museu de Geociências, Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080 - São Paulo, SP, Brazil, specimen number DR982
Empirical Formula of Type Material:
(Ba0.99K1.00 1.99(Na1.02Ca0.961.98(Mg0.95Mn0.051.00Nb6.02O19.00·6H2O
Geological Setting of Type Material:
Carbonatite
Associated Minerals at Type Locality:
Reference:
Andrade, M.B., Atencio, D., Menezes Filho, L.A.D., Spratt, J. (2018) Melcherite, trigonal Ba2Na2Mg[Nb6O19].6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine: 82: 111-120.

Synonyms of MelcheriteHide

Fluorescence of MelcheriteHide

Non-fluorescent

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for MelcheriteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Andrade, M.B., Atencio, D. and Menezes Filho, L.A.D. (2015) Melcherite, IMA 2015-018. CNMNC Newsletter No. 25, June 2015, page 535. Mineralogical Magazine: 79: 529-535.
IMA Newsletter No. 29 ("Soon after the approval of the new mineral melcherite (IMA No. 2015-018; see CNMNC Newsletter 25), the authors of the proposal have communicated results of subsequent analytical work on this mineral, which verifies essential contents of sodium. The new data were examined carefully by the CNMNC officers and were found reliable. The revised simplified formula, Ba2Na2Mg[Nb6O19]·6H2O, has been approved executively.")
Andrade, M.B., Atencio, D., Menezes Filho, L.A.D., Spratt, J. (2018) Melcherite, trigonal Ba2Na2Mg[Nb6O19].6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine: 82: 111-120.

Internet Links for MelcheriteHide

Localities for MelcheriteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Brazil (TL)
 
  • São Paulo
    • Cajati
Andrade, M.B., Atencio, D. and Menezes Filho, L.A.D. (2015) Melcherite, IMA 2015-018. CNMNC Newsletter No. 25, June 2015, page 535; Mineralogical Magazine, 79, 529-535; Andrade, M.B., Atencio, D., Menezes Filho, L.A.D., Spratt, J. (2018): Melcherite, trigonal Ba2Na2Mg[Nb6O19].6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine: 82: 111-120.
Mineral and/or Locality  
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